Technical Field
This disclosure principally relates to a circuit board testing apparatus. More specifically, the disclosure relates to an apparatus for detecting if sparking and partial discharge occurs between wiring patterns on the printed circuit board when voltage is applied between the wiring patterns. If so, the printed circuit board may be rejected as having insufficient insulating properties.
Related Art
A known testing apparatus performs a test to determine the state of insulation between wiring patterns formed on a circuit board (i.e., as to whether a satisfactory insulation property is ensured), thereby determining whether the circuit board is a non-defective product. The test as to the insulation state involves applying a predetermined voltage to a pair of wiring patterns to be tested, and measuring a resistance value between the wiring patterns.
During such insulation test, sparking may occur between the wiring patterns because of the voltage applied to the wiring patterns. In the case where sparking occurs, there is a high possibility that the circuit board sustains some damage. Accordingly, it is preferred that a circuit board at which sparking occurs in the test be identified as a defective product.
In this respect, Japanese Patent No. 3,546,046 discloses a configuration for detecting occurrence of sparking, by detecting a trailing edge of a voltage waveform applied to a wiring pattern (i.e., by detecting a point at which a voltage becomes lower than a preceding voltage). The configuration disclosed in Japanese Patent No. 3,546,046 is capable of ensuring that a circuit board at which sparking during an insulation test is prevented from being mixed with non-defective products.
Recently, the pattern pitch on a printed circuit board has become narrower year by year. Hence, a partial electrical discharge may occur more frequently between wiring patterns during an insulation test. Also in the case where a partial discharge occurs, a circuit board may sustain damage. As in the case of a circuit board at which sparking occurs during the insulation test, it is preferred that a circuit board at which partial discharge occurs is identified as a defective product.
Unlike the case of sparking however, a trailing edge of a voltage is not observed in the case of partial discharge because only a small current is fed between the wiring patterns when there is a partial discharge. Hence, the configuration disclosed in Japanese Patent No. 3,546,046 is incapable of detecting if a partial discharge occurs during the insulation test.